1. Field of the Invention
The present invention generally relates to a method for forming a semiconductor device having a fin structure, and more specifically, to a method for forming a semiconductor device having a fin structure which comprises etching a silicon substrate with a recess gate mask and performing a selective etching process on a device isolation film having a double oxide film structure.
2. Description of the Related Art
A conventional method for forming a semiconductor device having a fin structure is performed as follows.
First, a device isolation oxide film is formed over a silicon substrate, and then ions are implanted into a cell region to form a well.
The silicon substrate of an active area is etched using a recess gate mask.
The device isolation oxide film is etched using a fin mask.
A gate oxide film is formed over the entire surface of the resulting structure.
A polysilicon layer, a tungsten silicide layer and a hard mask nitride film are deposited over the entire surface of the resulting structure to form a gate electrode.
Since the device isolation oxide film is over-etched using a fin mask to form a fin structure according to the conventional method, polysilicon in a dummy fin affects an active storage node, thereby degrading electric characteristics. Furthermore, since the recess gate mask and the fin mask are both used, the process is complicated, and accuracy is degraded.